1. Field of the Invention
This invention relates to a semiconductor device manufacturing apparatus and semiconductor device manufacturing method for forming semiconductor elements (semiconductor chips) by dividing a semiconductor wafer. More particularly to an affixing technique for adhesive tapes when the semiconductor wafer is divided.
2. Description of the Related Art
Conventionally, the process for forming semiconductor elements (semiconductor chips) by dividing a semiconductor wafer is performed according to the steps shown in FIGS. 1 and 2, for example. First, as shown in FIG. 1, an adhesive tape (holding tape) 12 is affixed to the rear surface of a semiconductor wafer 11 on which elements have been formed. The adhesive tape 12 has larger size than the semiconductor wafer 11 and is mounted on a wafer ring 13 so as to be easily handled when it is transferred or mounted on a manufacturing apparatus. Next, the semiconductor wafer 11 is divided into discrete semiconductor elements 11-1, 11-2, 11-3, . . . . In FIG. 1, a diamond blade 14 is used to divide the semiconductor wafer. However, the dividing method is not limited to a mechanically dividing method and can be attained by use of various methods of mechanical grinding and breaking (cleaving), scribing and breaking, application of laser beam, application of laser beam and breaking, and the like.
The semiconductor wafer 11 which is divided into the discrete semiconductor elements 11-1, 11-2, 11-3, . . . is transferred while it is held by the wafer ring 13 and adhesive tape 12 as shown in FIG. 2.
After this, the semiconductor elements 11-1, 11-2, 11-3, . . . are sequentially picked up from the adhesive tape 12 affixed to the rear surface of the semiconductor wafer 11. The picking-up process is performed while the adhesive tape 12 is expanded to widen gaps between the semiconductor elements 11-1, 11-2, 11-3, . . . or the picking-up process is performed without widening the gaps. After the thus picked-up semiconductor element is mounted on a lead frame or TAB tape, it is sealed into a resin or ceramic package to complete a semiconductor device.
When the semiconductor elements are made thin, the adhesive tape is peeled from the rear (or back-side) surface of the semiconductor wafer 11 and an adhesive tape is affixed to the front surface thereof as shown in FIG. 4 after the semiconductor wafer 11 is divided into the discrete semiconductor elements 11-1, 11-2, 11-3, . . . as shown in FIG. 3. The semiconductor wafer 11 which is held by an adhesive tape 15 and wafer ring 16 is transferred to and set on the table of a grinding attachment. Then, as shown in FIG. 5, the rear surface of the semiconductor wafer 11 is ground by use of a grindstone and polished by use of free adhesive grains or partly removed by etching or the like so that the semiconductor wafer will be made thin.
The above conventional manufacturing technique is described in Jpn. Pat. Appln. KOKAI Publication No. 11-40520 and Japanese Patent Specification No. 3024384, for example.
In this example, a case wherein the wafer ring 13 (and 16) is used is explained. However, it is also possible to cut and divide the wafer 11 while the wafer 11 is held only by use of the adhesive tape 12 without using the wafer ring 13 as shown in FIG. 6 and then transfer the wafer with the discrete semiconductor elements 11-1, 11-2, 11-3, . . . affixed to the adhesive tape 12 as shown in FIG. 7. Further, it is possible to grind the rear surface of the semiconductor wafer 11 while the wafer 11 is held only by use of the adhesive tape 15.
In recent years, in order to increase the number of semiconductor elements obtained from each semiconductor wafer, the width of lines at the time of dividing of the semiconductor wafer is made small. Further, it is required to make the thickness of finally obtained semiconductor elements extremely thin, for example, less than 100 μm and it is indispensable to suppress damages occurring when the semiconductor wafer is cut and discretely divided.
However, with the above conventional semiconductor device manufacturing apparatus and semiconductor device manufacturing method, the following problems occur.
First, if the cutting gaps are narrow when the semiconductor wafer is divided into discrete semiconductor elements, the semiconductor elements 11-1, 11-2, 11-3, . . . which are adjacent to one another interfere with one another at the transferring time as shown in FIGS. 8A and 8B. FIG. 8A shows stress applied at the transferring time and FIG. 8B shows an area surrounded by broken lines 18 in FIG. 8A. By the above interference, damages such as chippings 19A and scratches 19B occur on the front surface portion and side surface portion of the semiconductor element 11-1 as shown in FIG. 9. As a result, when a semiconductor device is formed by performing a pick-up process and mounting process after this, chip cracks will occur starting from the chippings 19A or scratches 19B and the semiconductor device will be defective.
Further, as shown in FIG. 10, at the back-side grinding time, discrete semiconductor elements 11-1, 11-2, . . . interfere with one another and damages such as chippings 19A and scratches 19B occur on the side surface portion and rear surface portion of the semiconductor elements 11-1, 11-2, . . . as shown in FIG. 11. Therefore, when a semiconductor device is formed as a product by performing a pick-up process and mounting process, chip cracks are more likely to occur, thereby lowering the quality and lowering the manufacturing yield.
Particularly, if a breaking (cleavage) method is used to divide the semiconductor wafer, substantially no gap is provided between the discrete semiconductor elements 11-1, 11-2, 11-3, . . . , and therefore, the above problem of occurrence of damages such as chippings and scratches due to interference between the semiconductor elements becomes significant.